New Appoaches to Inspection Planning of Fatigue Damaged Offshore Platforms

Abstract The present paper summarizes the results of research and development efforts over the last approximately five years to develop simplified and practically applicable approaches for reliability and risk based inspection planning. These efforts have led to the development of a generic inspection planning approach. Following the approach the fatigue sensitive details are categorized and described generically according to standard design parameters such as the Fatigue Design Factor (FDF) and the SN curve. When a measure of the structural consequences of fatigue failure e.g. the RSR and the corresponding probability of structural collapse given fatigue failure of the considered detail are known, generic inspection plans may derived as a function of the generic parameters together with the relative cost of inspections, repairs and failures. Due to the simplicity of the format of the developed inspection plans, the proposed approach has a high potential to be used in codes for the design and maintenance of steel structures. The validity of the proposed approach is illustrated through a study regarding inspection planning of a tri-pod offshore structure where generic inspection plans are obtained using two approximations, namely assuming equidistant inspection intervals and using constant thresholds for the annual probability of failure.